Uncovering the history of Islamicate astronomy

Gastbeitrag von Dr. Scott Trigg

Long before our current scientific understanding of the solar system, astronomers as far back as ancient Babylonia recorded observations of the night sky. In an Earth-centered cosmos, the entirety of the heavens seems to rotate around the stationary Earth in a daily motion of rising and setting. However, by observing the stars at the horizon before sunrise or after sunset, it quickly becomes apparent that the Sun, Moon, and planets all have their own irregular motions against the background of the constellations. The challenge ancient Hellenistic astronomers set themselves was to account for this collection of irregular motions by means of a system of uniform circular motions, the only motion considered appropriate to the perfect, eternal celestial bodies. Their efforts resulted in the Almagest of Claudius Ptolemy (2nd c. CE), a masterpiece of mathematical modeling that remained the preeminent text in astronomy for over a millennium, and the standard against which later models were evaluated.

Centuries later, after the appearance of Islam and the emergence of new societies throughout the Mediterranean, Middle East, and Central Asian world, mathematicians and astronomers translated the Almagest into Arabic and began studying it. They raised a number of criticisms and established new observatories to produce updated observations and calculations, all of which led to an innovative tradition of astronomy in the medieval Islamicate world. These texts were produced as handwritten manuscripts and many remain unstudied, but the Staatsbibliothek zu Berlin Oriental Department holds a large collection of manuscripts that is being used by historians of science to understand the rich heritage of Islamicate astronomy. Some manuscripts were dedicated to rich patrons, while others were produced for students and may contain unique marginal notes. All of them hold the potential to provide insights into how astronomical knowledge was taught, criticized, and applied in different locations across Islamicate societies.

Ptolemy’s models were described in terms of flat, two-dimensional circles rather than physical structures in the heavens. However, according to Islamicate astronomers only physical bodies, not “imaginary” circles, could produce motion. Their goal was to maintain or improve the predictive accuracy of Ptolemy’s models, but with a system in which the mathematical models describing the planetary motions could correspond to three-dimensional spheres. Moreover, in order to make accurate predictions, Ptolemy’s models all involved various violations of the principle of uniform circular motion. These issues became all the more pressing to Islamicate astronomers, who argued on philosophical and physical grounds that the celestial spheres simply could not produce the motions Ptolemy described. As a result, Islamicate astronomers produced a series of texts and commentaries setting forth their criticisms of the Almagest models and proposed the implementation of new models that would correct its flaws.

Two episodes in this history stand out in particular, the flowering of scientific communities at the cities of Maragha (in modern-day Iran) in the 13th c. and Samarqand (in modern-day Uzbekistan) in the 15th c. At Maragha, the Islamic astronomer and theologian Nasir al‑Din al‑Tusi prevailed upon the grandson of the Mongol conqueror Chingiz Khan to establish an astronomical observatory. Tusi and other prominent scientists carried out a program of observations that led to the production of an up-do-date table of astronomical data, known as Zij-i Ilkhan-i, which could be used for regulating time and the calendar, predicting eclipses, and calculating other celestial motions for applications such as astrology. Moreover, the scientists discussed ways to correct Ptolemy’s models. Prior to arriving at Maragha, Tusi had already developed a mathematical construction, known today as the “Tusi Couple”, that used the combined motion of two spheres to produce an oscillating motion, which he used to correct problems in the models for the Moon and planets. One of his colleagues invented an alternative mathematical device, the “Urdi Lemma,” which could accomplish similar results. These astronomers described their arguments and ideas in texts, such as Tusi’s al‑Tadhkira fi ‘ilm al‑hay’a (“Memoir on Astronomy”), which were studied and commented on by following generations.

Illustration of Tusi Couple from Nasir al-Din al-Tusi’s al-Tadhkira fi ‘ilm al-hay’a, MS Or. oct. 3568, fol 18b

Illustration of Tusi Couple from Nasir al-Din al-Tusi’s al-Tadhkira fi ‘ilm al-hay’a. – Staatsbibliothek zu Berlin, MS. Or. oct. 3568, detail of fol. 18b – CC BY‑SA 4.0

The 15th c. observatory at Samarqand was another significant center of astronomical and scientific activity. It was established by a Sultan of the Timurid dynasty, Ulugh Beg, who in addition to providing funding and support for the observatory and scholars, was himself a highly skilled mathematician. Ulugh Beg gathered astronomers from across the Middle East and Central Asia to his court, and in addition to the revised table of astronomical data they produced we are fortunate to have recorded anecdotes about scholarly life in Samarqand in the form of letters written by the first director of the observatory, as well as a commentary on Tusi’s Tadhkira written by an advanced student, Fathallah al‑Shirwani. These texts, along with other commentaries on the Tadhkira and on related astronomical texts, attest to a dynamic and creative engagement with astronomical problems and to debates within philosophy and theology on the relationship between God, the natural world, and the ability of humans to apply our intellects, experiences, and even experimentation to understand the fundamental order underneath the seemingly unpredictable phenomena we encounter.

Historians are still examining the hundreds of unstudied astronomical manuscripts from this period, but their work should already convince us to reject the old story of a “Golden Age” of Islamicate science followed by a period of “Decline”. In fact, as evidenced by the texts and commentaries produced by scholars at sites such as Maragha and Samarqand, the scientific enterprise continued at a high level of creativity and technical proficiency for centuries longer than previously imagined.


Herr Dr. Scott Trigg, Society of Fellows in the Humanities, The University of Hong Kong, war im Rahmen des Stipendienprogramms der Stiftung Preußischer Kulturbesitz im Jahr 2019 als Stipendiat an der Staatsbibliothek zu Berlin. Forschungsprojekt: “Astronomy and Theology in the post-Classical Islamic Commentary Tradition at Samarqand”

Time Unfolded: A Late Medieval Concertina Calendar in the Staatsbibliothek zu Berlin (Libr. pict. A 92)

Gastbeitrag von Dr. Sarah M. Griffin

The diffusion of mechanical clocks in fourteenth-century Europe introduced new systems of tracking time. Many of these converged in late medieval calendars, which contain details of the yearly cycle that were calculated by astronomical observation and ordered through liturgical routine. During this period, the calendar broke free from its traditional book form and came to be found in scrolls, almanacs, atlases, printed books, disks within astronomical clocks, painted triptychs and even hunting knives. A particularly interesting example of these new forms are concertina calendars: manuscripts that included pictorial expressions of the calendar that could be folded out like an accordion in order to be read.

The Staatsbibliothek zu Berlin houses one of these rare manuscripts: Libr. pict. A 92 (available to view online), which I have come to call the ‘Berlin calendar’. Made around 1400 in central Germany, the Berlin calendar consists of one large, folded piece of vellum. On one side is a pictorial saints’ calendar (a month of which is shown in the banner above) where the most important feast days are illustrated. Usually they are depicted as the bust of a saint who is celebrated on that day, such as Saint Barbara on the left, who holds a tower. On the other side of the vellum (image 1) are the labours of the months, each undertaking an activity suitable for that month, and signs of the zodiac accompanied by curious circular diagrams that, through their varying degrees of fullness, express the average hours of daylight and darkness for each month. The latter are particularly revealing as to contemporary time-keeping practises.

Image 1

Image 1: Labours of the months and wheels of daylight and darkness from January to March. – Detail of Staatsbibliothek zu Berlin, Libr. pict. A 92, Germany (c. 1400) – Public Domain

During a two-month stay at the Staatsbibliothek from July to August 2019, I tasked myself to better understand the Berlin calendar and how it would have been used in the Middle Ages by considering it within a group of similar concertinas. In addition to forming a focused analysis of the function of concertina manuscripts, their study informed a larger project on the role of different forms of calendar in daily time-keeping during the fifteenth century.

Concertina manuscripts, sometimes referred to as accordion books, provide rich and fascinating insight into the reading practices of the later Middle Ages while showing the potential of the manuscript medium to render complex and interactive three-dimensional forms. They must be unfolded to be read, and are designed in such a way that they can be unfolded in various orientations to reveal different sets of content. This structure provided the medieval maker with the potential to link different pockets of information through the multiple ways in which the manuscript could be folded and unfolded. The Berlin calendar is a particularly important manuscript for the understanding of how concertinas were read because it is still in its folded form, whereas many others have been unfolded and mounted onto boards to ensure they cannot be folded again. Although the manuscript has been digitised, it was absolutely essential that it was consulted in the flesh for the multiple patterns of its unfolding to be understood. The fragility of the parchment and the repetitive unfolding and refolding of its parts meant it could only be consulted four times over the Summer, making my time with the manuscript even more precious.

Image 2: Detail of Staatsbibliothek zu Berlin, Libr. pict. A 92, Germany (c. 1400), unfolding February, Photo: Sarah Griffin; CC-BY-NC-SA

Image 2: Detail of Staatsbibliothek zu Berlin, Libr. pict. A 92, Germany (c. 1400): Unfolding February. – Photo: Sarah Griffin; CC-BY-NC-SA

Research on folded medieval manuscripts has flourished in recent years, thanks in part to the publication of J. P. Gumbert’s ‘Bat Books’: a catalogue of folded manuscripts that Gumbert worked on from the 1990s onwards, only to be published shortly before his death in 2016. Gumbert managed to consult almost every single of the sixty‑three folded manuscripts surviving, barring just three. From his first-hand experience of their handling, he created the wonderful term ‘bat book’ to describe them, as ‘when in rest they hang upside-down and all folded up, but when action is required they lift up their heads and spread their wings wide’. Gumbert’s work led me to study concertinas in other collections, including a Dutch concertina calendar in the Germanisches Nationalmuseum (Nuremburg) made almost contemporaneously to that now in Berlin.

By consulting these calendars both in person and online I was able to identify eight manuscripts (from Gumbert’s twenty‑one concertinas) that share the same model. Studying the Berlin calendar within this group was like piecing together a three-dimensional jigsaw puzzle. I used the content and layout of the other manuscripts to evaluate which parts of the Berlin calendar were missing, if any at all. As well as providing potential sources for it, the unique features of the Berlin calendar could also be identified. Not only is it the only surviving German concertina, it is also the only calendar not to contain the Golden Numbers, which are essential to calculate the moveable feast dates, such as Easter. This raises the question of whether it is unfinished or whether it was made for a different purpose. The findings of this research will form an article on the reading practices of this particular model of concertina calendar and where the Berlin calendar fits into the group.

In addition to informing this dedicated study, the two-month stay in Berlin allowed me to visit other German collections that hold objects of primary significance to the larger project. Building upon previous research on a monumental calendar from Verona that is associated with the earliest astronomical clocks (the published outcome of which is available online), I was glad to consult a large wooden calendar disk made for Lübeck’s first astronomical clock, originally in the Marienkirche (Lübeck, St. Annen‑Museum, c. 1461, Inv. no. 1892‑145); a large calendar volvelle in the form of a triptych (Nuremburg, Germanisches Nationalmuseum, 1461, Inv. no. WI58); and a sixteenth-century hunting knife made by Ambrosius Gemlich, into which he etched a beautifully-detailed liturgical calendar (Munich, Bayerisches Nationalmuseum, Inv. no. 13/1174, see image 3). However, it was not always necessary to leave Berlin. The Staatsbibliothek houses many other calendrical curiosities, including a sixteenth-century wooden calendar (Libr. Pict. A 75, see image 4) whose saints’ calendar is similar in format to the Berlin calendar.

Image 3: Munich, Bayerisches Nationalmuseum, Inv. no. 13/1174, sixteenth century, calendar etched into a hunting knife by Ambroisius Gemlich, detail of January, February, April and May, Photo: Sarah Griffin; CC-BY-NC-SA

Image 3: Calendar etched into a hunting knife by A. Gemlich, 16th c.: Detail of January, February, April and May. – Munich, Bayerisches Nationalmuseum, Inv. no. 13/1174 – Photo: Sarah Griffin; CC-BY-NC-SA


Image 4: Staatsbibliothek zu Berlin, Libr. pict. A 75, sixteenth century, Detail of wooden calendar showing February, Photo: Sarah Griffin; CC-BY-NC-SA

Image 4: Detail of wooden calendar showing February, 16th c. – Staatsbibliothek zu Berlin, Libr. pict. A 75 – Photo: Sarah Griffin; CC-BY-NC-SA
















From the selection of calendars mentioned above, one can observe the variety of forms in which they were crafted during this period. Their first-hand analysis can reveal how time was ordered and understood in the late Middle Ages, a period defined by the introduction of mechanical time-keeping and in which the methods of measuring time were in transition.


Associated sources:

P. J. Becker, Aderlaß und Seelentrost: Die Überlieferung deutscher Texte im Spiegel Berliner Handschriften und Inkunabeln (Mainz, 2003), pp. 378‑80, no. 181

J. Borland, ‘Moved by Medicine: The Multisensory Experience of Handling Folded Almanacs’, in Sensory Reflections: Traces of Experience in Medieval Artifacts, ed. by F. Griffiths and K. Starkey (Berlin, 2018), pp. 204‑24.

S. M. Griffin, ‘Synchronising the Hours: A fifteenth-century wooden volvelle from the Basilica of San Zeno, Verona’, in Journal of the Warburg and Courtauld Institutes, LXXXI (Dec., 2018), pp. 31‑67

J. P. Gumbert, Bat Books: A Catalogue of Folded Manuscripts Containing Almanacs or Other Texts (Turnhout, 2016)

Erik Kwakkel, ‘The Incredible Expandable Book’, accessible at medievalbooks,

C. Silva, ‘Opening the Medieval Folding Almanac’, in Exemplaria, 30:1 (2018), pp. 49‑65

R. Wieck, The Medieval Calendar: Locating Time in the Middle Ages (New York, 2017)


Frau Dr. Sarah M. Griffin, Winchester College, war im Rahmen des Stipendienprogramms der Stiftung Preußischer Kulturbesitz im Jahr 2019 als Stipendiatin an der Staatsbibliothek zu Berlin. Forschungsprojekt: “Hours of Daylight, Hours of Darkness: The Visualisation of Time in a Late Medieval Almanac (Libr. pict. A 92)”